154 LIVERPOOL BIOLOGICAL SOCIETY. 
albumen and pigment, and differ chiefly in physiological 
respects. The third kind contains granules of calcium 
phosphate. The salivary glands have been described by 
Nalepa (7) and Bergonzini (26) as consisting of unicellular 
glands. ‘These cells form groups, each of the groups 
enclosed by a membrane. 
Descriptions of the radula in Limaz are to be found in 
most text-books of Zoology, and so I shall refer only to 
the more recent papers of Rossler (32) on the formation of 
the radula, and Dybowski (27) studies on the structure 
of the radula in Limaz and other Stylommatophora. In 
regard to the mode of its movement, however, I have to 
make some remarks. Cuvier (2) originally stated that in 
chewing the radular sac is moved first by the retractors of 
the mouth. This radular sac is the ventral diverticulum 
at the posterior end of the buccal mass, in which the 
termination of the radula lies imbedded. It is more or 
less connected with the cartilage which supports the 
radula. When therefore the muscles are put in action, 
the radula sac is first moved, then the cartilage, and thus 
finally the radula. The cartilage together with the radula 
performs a kind of peristaltic movement, and the food- 
particles which had been cut to pieces by the jaw (!) are 
seized, as if by a toothed wheel, and are carried back to 
the entrance of the esophagus: Such were Cuvier’s views. 
Huxley’s opinion differs greatly from that of Cuvier. 
He distinguishes two kinds of muscles: intrinsic muscles, 
which connect the cartilage and the subradular membrane, 
by their action the radula is drawn over the supporting 
cartilage backwards and forwards like a chain-saw; and 
- extrinsic muscles, which connect the cartilage with the 
lateral walls of the head. ‘They move the ‘chewing 
apparatus (odontophore) as a whole, and thus a licking 
motion is performed. Huxley, however, mentions the 
